1. Field of the Invention
The present disclosure relates to a lighting system using a lighting device which has a light-emitting diode (LED) as a light source.
2. Description of the Related Art
The LED is widely used as a light source for various electric devices such as lighting devices because the LED emits high-brightness light with a low electric power. The LED used for lighting devices generates much heat when the LED emits high-brightness light, for example. Light emission characteristics of an LED are deteriorated when the LED is subjected to high temperature conditions, and the LED is damaged by heat in some cases.
To address this issue, a lighting device which has an LED as a light source is generally attached with a heat dissipation device having a heat dissipation property responsive to the light emission characteristics of the LED. However, if the heat dissipation device is deteriorated with time or does not have an appropriate thermal resistance value corresponding to the light emission characteristics of the LED, the heat generated by the LED is not properly dissipated, and the LED is damaged in some cases.
For example, Unexamined Japanese Patent Publication No. 2004-319595 discloses a lighting device in which temperature of a substrate on which an LED is mounted and temperature of a heatsink are detected to monitor secular change of the heat dissipation property, based on a thermal resistance value between the substrate and the heatsink. Unexamined Japanese Patent Publication No. 2011-181295 discloses a lighting device having a characteristics setting unit in which the characteristics of the LED are previously set.